The present invention relates generally to integrated circuits and, more particularly, to integrated circuits (ICs) and IC design structures in which through silicon via (TSV)-induced stresses in a substrate are reduced.
In many known ICs, TSVs are placed throughout the IC in order to facilitate the connection of IC devices. Typically, such TSVs are provided in “cells” comprising one or more TSV. Each TSV in a cell includes a longitudinal axis and, where more than one TSV is included in a cell, their longitudinal axes are typically arranged in a substantially parallel direction.
For example, FIG. 1 shows a schematic representation of a portion of a surface of an IC 100 as may exist in an IC design file, wherein the IC 100 includes a substrate 10 and a plurality of TSV cells 20A-D, 22A-D, 24A-D spaced throughout the surface of IC 100. Each TSV cell includes a plurality of TSVs 30A, 32A, 34A, 36A, 38A oriented substantially parallel to each other. For the sake of simplicity, only TSVs 30A, 32A, 34A, 36A, 38A in TSV cell 20A are labeled in FIG. 1.
Typically, the orientation of TSVs in a TSV cell is referred to as “horizontal” or “vertical.” Such terms are meant to refer only to the orientations of TSVs in one TSV cell as compared to an orientation of TSVs in another TSV cell. For example, in FIG. 1, the orientation of TSVs 30A, 32A, 34A, 36A, 38A of TSV cell 20A and of TSV cell 20A as a whole may be referred to as “horizontal,” whereas orientation of TSV cell 20D and its TSVs may be referred to as “vertical.” Other designations may be used to refer to such relative orientations, including, for example, “North-South” and “East-West.”
In some ICs, whether a particular TSV cell is oriented horizontally or vertically may be of importance. In many cases, however, the orientation of particular TSV cells is not of great importance and is more likely the result of convention or simplicity in IC design. As a consequence, it is not uncommon for an IC to include multiple adjacent TSV cells having the same orientation.
For example, referring again to FIG. 1, it can be seen that TSV cells 20A, 20B, and 20C are all oriented horizontally. In addition, TSV cells 20D, 22D, and 24D, as well as TSV cells 22B and 24B are all oriented vertically. Such similar orientation of adjacent TSV cells will result in increased stresses 40, 42, 50, 52, 54 in substrate 10 caused, at least in part, by differences in the thermal expansions of substrate 10 and the materials used to fill the TSVs, typically copper, tungsten, or doped polysilicon. In effect, the orientation of adjacent TSVs in the same direction acts much like a wedge within substrate 10 as the TSV materials thermally expand more quickly and/or to a greater extent than the material of substrate 10.